A Pakistani official says a package containing deadly anthrax was mailed last year to the office of Pakistani Prime Minister Yousuf Raza Gilani.

A spokesman for Mr. Gilani said Wednesday tests conducted at a laboratory after the package arrived in October of 2011 determined that it contained anthrax.

The package was mailed from the town of Jamshoro in the southern Pakistani province of Sindh. There were no reported casualties.

Pakistani police are investigating the case. They originally said the package was sent several weeks ago to Mr. Gilani.

Officials gave no immediate word on who may be responsible.

Islamic militants have not been known to send letters or packages containing toxic material.